U.S. patent number 10,157,953 [Application Number 15/624,055] was granted by the patent office on 2018-12-18 for image sensing device and manufacturing method thereof.
This patent grant is currently assigned to TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.. The grantee listed for this patent is TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD.. Invention is credited to Jian-Ming Chen, Chih-Chang Huang, Yao-Hsiang Liang, Chi-Ming Lu, Jung-Chih Tsao.
United States Patent |
10,157,953 |
Huang , et al. |
December 18, 2018 |
Image sensing device and manufacturing method thereof
Abstract
Some embodiments of the present disclosure provide a back side
illuminated (BSI) image sensor. The back side illuminated (BSI)
image sensor includes a semiconductive substrate and an interlayer
dielectric (ILD) layer at a front side of the semiconductive
substrate. The ILD layer includes a dielectric layer over the
semiconductive substrate and a contact partially buried inside the
semiconductive substrate. The contact includes a silicide layer
including a predetermined thickness proximately in a range from
about 600 angstroms to about 1200 angstroms.
Inventors: |
Huang; Chih-Chang (Chiayi,
TW), Lu; Chi-Ming (Kaohsiung, TW), Chen;
Jian-Ming (Chiayi, TW), Tsao; Jung-Chih (Tainan,
TW), Liang; Yao-Hsiang (Hsinchu, TW) |
Applicant: |
Name |
City |
State |
Country |
Type |
TAIWAN SEMICONDUCTOR MANUFACTURING COMPANY LTD. |
Hsinchu |
N/A |
TW |
|
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Assignee: |
TAIWAN SEMICONDUCTOR MANUFACTURING
COMPANY LTD. (Hsinchu, TW)
|
Family
ID: |
57128948 |
Appl.
No.: |
15/624,055 |
Filed: |
June 15, 2017 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20170294473 A1 |
Oct 12, 2017 |
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Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
Issue Date |
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14689838 |
Apr 17, 2015 |
9691804 |
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L
27/14698 (20130101); H01L 27/14621 (20130101); H01L
27/14645 (20130101); H01L 21/76843 (20130101); H01L
27/14636 (20130101); H01L 21/76889 (20130101); H01L
27/1464 (20130101); H01L 27/1463 (20130101); H01L
27/14612 (20130101); H01L 27/14625 (20130101); H01L
21/76856 (20130101); H01L 27/14685 (20130101); H01L
21/76802 (20130101); H01L 27/14623 (20130101); H01L
27/14689 (20130101); H01L 27/14627 (20130101) |
Current International
Class: |
H01L
27/146 (20060101); H01L 21/768 (20060101) |
References Cited
[Referenced By]
U.S. Patent Documents
Other References
Office action and search report issued by the China State
Intellectual Property Office dated Jun. 4, 2018 for corresponding
application 201510759461.1. cited by applicant.
|
Primary Examiner: Ahmad; Khaja
Attorney, Agent or Firm: WPAT, P.C., Intellectual Property
Attorneys King; Anthony
Parent Case Text
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is a divisional of U.S. application Ser. No.
14/689,838, filed on Apr. 17, 2015, and claims priority thereto.
Claims
What is claimed is:
1. A method of manufacturing a back side illuminated (BSI) image
sensor, comprising: receiving a semiconductive substrate; forming a
dielectric layer on a front side of the semiconductive substrate;
forming a recess in the dielectric layer such to expose the front
side; forming a titanium layer inside the recess and on the front
side of the semiconductive substrate by using a plasma ignition
power in a predetermined range from about 600 watts to 900 watts;
performing a first thermal anneal; performing a second thermal
anneal; and forming a barrier layer inside the recess; wherein the
performing the second thermal anneal comprises forming a silicide
layer comprising a lattice structure, and the lattice structure
comprising a {220} plane or a {311} plane configured to be measured
with peaks on an X-ray diffraction pattern of the lattice
structure.
2. The method of claim 1, wherein the forming the titanium layer
comprises using a first plasma power maintained substantially
constant at a first predetermined range lesser than half of the
predetermined range.
3. The method of claim 2, wherein the forming the titanium layer
comprises using a second plasma power maintained substantially
constant at a second predetermined range proximately double the
first predetermined range but lower than the predetermined
range.
4. The method of claim 1, wherein the performing the second thermal
anneal comprises forming a silicide layer comprising a
predetermined thickness proximately in a range from about 600
angstroms to about 1200 angstroms.
5. The method of claim 1, further comprising removing an unreacted
titanium between the first thermal anneal and the second thermal
anneal.
6. A method of manufacturing a back side illuminated (BSI) image
sensor, comprising: receiving a semiconductive substrate; forming a
dielectric layer on a front side of the semiconductive substrate;
forming a recess in the dielectric layer to expose the front side;
forming a titanium layer inside the recess and on the front side of
the semiconductive substrate by using a plasma ignition power in a
predetermined range; performing a first thermal anneal; and
performing a second thermal anneal to form a silicide layer
comprising a lattice structure, and the lattice structure
comprising a {220} plane configured to be measured with peaks on an
X-ray diffraction pattern of the lattice structure.
7. The method of claim 6, wherein the receiving the semiconductive
substrate comprises receiving the semiconductive substrate
including a non-silicide portion.
8. The method of claim 6, wherein the forming the titanium layer
comprises using a first plasma power maintained substantially
constant at a first predetermined range lesser than half of the
predetermined range.
9. The method of claim 7, wherein the forming the titanium layer
comprises using a second plasma power maintained substantially
constant at a second predetermined range proximately double the
first predetermined range but lower than the predetermined
range.
10. The method of claim 7, wherein the performing the first thermal
anneal comprises causing the titanium layer in a bottom portion of
the recess to react with the non-silicide portion in the
semiconductive substrate to form a silicide layer.
11. The method of claim 6, wherein the performing the second
thermal anneal comprises forming a silicide layer comprising a
predetermined thickness proximately in a range from about 600
angstroms to about 1200 angstroms.
12. The method of claim 6, further comprising removing an unreacted
titanium between the first thermal anneal and the second thermal
anneal.
13. A method of manufacturing a back side illuminated (BSI) image
sensor, comprising: receiving a semiconductive substrate including
a non-silicide portion; forming a dielectric layer on a front side
of the semiconductive substrate; forming a recess in the dielectric
layer to expose the front side; forming a titanium layer inside the
recess and on the front side of the semiconductive substrate by
using a plasma ignition power in a predetermined range; performing
a first thermal anneal to cause the titanium layer in a bottom
portion of the recess to react with the non-silicide portion in the
semiconductive substrate to form a silicide layer having a
crystallographic structure of C49; and performing a second thermal
anneal to change the crystallographic structure of the silicide
layer from C49 to C54; wherein the performing the second thermal
anneal comprises forming the silicide layer having a lattice
structure, including a {311} plane configured to be measured with a
peak on an X-ray diffraction pattern of the lattice structure.
14. The method of claim 13, wherein the forming the titanium layer
comprises using a first plasma power maintained substantially
constant at a first predetermined range lesser than half of the
predetermined range.
15. The method of claim 14, wherein the forming the titanium layer
comprises using a second plasma power maintained substantially
constant at a second predetermined range proximately double the
first predetermined range but lower than the predetermined
range.
16. The method of claim 13, wherein the performing the second
thermal anneal comprises forming the silicide layer comprising a
predetermined thickness proximately in a range from about 600
angstroms to about 1200 angstroms.
17. The method of claim 13, further comprising removing an
unreacted titanium between the first thermal anneal and the second
thermal anneal.
18. The method of claim 13, wherein the performing the second
thermal anneal comprises forming the silicide layer having a
lattice structure, including a {220} plane configured to be
measured with a peak on an X-ray diffraction pattern of the lattice
structure.
19. The method of claim 1, wherein the performing the second
thermal anneal comprises: performing the second thermal anneal to
form a silicide layer; and planarizing the silicide layer such that
a top of the silicide layer is coplanar with the front side of the
semiconductive substrate.
20. The method of claim 13, further comprising: planarizing the
silicide layer such that a top of the silicide layer is coplanar
with the front side of the semiconductive substrate.
Description
FIELD
The present disclosure relates to a hack side illuminated (BSI)
image sensor.
BACKGROUND
Image sensors are widely used in various imaging applications and
products, such as cameras, scanners, photocopiers, etc. A
performance of an image sensor is depended on quality of pixels in
the image sensors. As a part of IC evolution for semiconductor
image sensors, the size of pixels has been steadily reduced. As the
size of pixels continue to shrink, quality of pixels become more
difficult to control.
The quality of pixels can affect performance such as an amount of
dark current. The dark current is one of sources for noise in the
image sensors. The dark current is referred to as a leakage current
in non-optical devices such as in transistors.
BRIEF DESCRIPTION OF THE DRAWINGS
Aspects of the present disclosure are best understood from the
following detailed description when read with the accompanying
figures. It is noted that, in accordance with the standard practice
in the industry, various features are not drawn to scale. In fact,
the dimensions of the various features may be arbitrarily increased
or reduced for clarity of discussion.
FIG. 1 is a plan view of an image sensor with some pixels, in
accordance with some embodiments of the present disclosure.
FIG. 2 is a cross-sectional of an image sensor, in accordance with
some embodiments of the present disclosure.
FIG. 3 is a cross-sectional view of an image sensor, in accordance
with some embodiments.
FIG. 4 is a cross-sectional view of an image sensor, in accordance
with some embodiments.
FIG. 5 is a cross-sectional view of an atomic structure, in
accordance with some embodiments.
FIG. 6 is diffraction patterns of atomic structures, in accordance
with some embodiments.
FIG. 7 is an operational flow of a method for manufacturing an
image sensor, in accordance with some embodiments.
FIG. 8 is an operational flow of a method for manufacturing an
image sensor, in accordance with some embodiments.
FIG. 13 is a diagram of an operation in a method for manufacturing
an image sensor, in accordance with some embodiments.
FIGS. 9 to 12 and 14 to 25 are cross sectional views of an
operation in a method for manufacturing an image sensor, in
accordance with some embodiments.
DETAILED DESCRIPTION
The following disclosure provides many different embodiments, or
examples, for implementing different features of the provided
subject matter. Specific examples of components and arrangements
are described below to simplify the present disclosure. These are,
of course, merely examples and are not intended to be limiting. For
example, the formation of a first feature over or on a second
feature in the description that follows may include embodiments in
which the first and second features are formed in direct contact,
and may also include embodiments in which additional features may
be formed between the first and second features, such that the
first and second features may not be in direct contact. In
addition, the present disclosure may repeat reference numerals
and/or letters in the various examples. This repetition is for the
purpose of simplicity and clarity and does not in itself dictate a
relationship between the various embodiments and/or configurations
discussed.
Further, spatially relative terms, such as "beneath," "below,"
"lower," "above," "upper" and the like, may be used herein for ease
of description to describe one element or feature's relationship to
another element(s) or feature(s) as illustrated in the figures. The
spatially relative terms are intended to encompass different
orientations of the device in use or operation in addition to the
orientation depicted in the figures. The apparatus may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein may likewise be
interpreted accordingly.
A performance of an image sensor is affected by a quality of a
pixel in the image sensor. The quality of the pixel is controlled
during a manufacture of the image sensor. A damaged pixel can cause
dark current and produce false image signal. A black pixel is a
pixel unable to produce electric current flowing through the image
sensor when photons are entering the image sensor. The black pixel
fails to produce a proper image signals. One of a cause of the
black pixel is a high resistance in a material for transmitting
electric signals in the image sensor. One of a place to reduce a
resistance in the image sensor is a silicide region between a
contact and a semiconductive substrate.
In FIG. 1, an image sensor 100 is illustrated. FIG. 1 is a
schematic plan view of an image sensor 100 in accordance with some
embodiments. The image sensor 100 includes a semiconductive
substrate 1. The semiconductive substrate 1 includes a pixel array
region 10 and a logic region 14 outside the pixel array region 10.
The pixel array region 10 includes one or more pixel regions 17 and
18 arranged therein in a pixel array. The pixel regions 17 and 18
are configured to convert light to image data. In some embodiments,
the pixel array region 10 includes complementary
metal-oxide-semiconductor (CMOS), and the image sensor 100 is a
CMOS image sensor (CIS). In some embodiments, the pixel regions 17
and 18 are charged coupled device (CCD) image sensors. In some
embodiments, the pixel regions 17 and 18 are monochromatic pixels.
In some other embodiments, the pixel regions 17 and 18 are color
pixels such as blue (B), green (G), or red (R) pixels configured to
detect different colors in an incident light. The image sensor 100
further includes one or more black level reference pixels 19
arranged in a black level reference pixel array 12. The black level
reference pixels 19 are similar or identical to the pixel regions
17 and 18, except that light is blocked to prevent the black level
reference pixels 19 from receiving light. Image data outputted by
the black level reference pixels 19 provides a black level that is
referenced for calibrating the image sensor 100. In some
embodiments, the black level reference pixels 19 are omitted.
FIG. 2 is a cross sectional view of image sensor 100. In some
embodiments, image sensor 100, 200, 300, or 500 in FIG. 2, 3, 4, or
9 is a back side illuminated (BSI) image sensor. The image sensor
100 includes the pixel array region 10 and black level reference
pixel array 12.
Pixel array region 10 includes pixel region 17 and pixel region 18.
The pixel regions 17 and 18 are separated by deep trench isolation
(DTI) 86. Pixel region 18 includes a transistor 2. The transistor 2
includes a gate structure 21, a gate spacer 25, a photosensitive
element 22, and a photosensitive element 23 or 22. Pixel region 17
and pixel region 18 are defined by the deep trench isolations DTI
86 at a boundary of pixel region 17 or 18. Semiconductive substrate
1 includes deep trench isolation (DTI) 86 at a back side S1 of the
semiconductive substrate 1. DTI 86 is under back side S1. A top
surface of DTI 86 is coplanar with hack side S1. A top surface of
protective layer 83 is above back side S1.
Black level reference pixel 19 is structured in black level
reference pixel array 12. A light shielding layer 752 is under the
capping layer 723. Light shielding layer 752 prevents incident
light 8 reaching the light shielding layer 752 from transmitting to
the photosensitive element 22 or 23. The photosensitive element 22
or 23 is coupled with the transistor 2. In some embodiments,
contact plug 53 is in proximity to a photo diode such as
photosensitive elements 22 or 23. The black level reference pixel
19 is configured to output image data from the transistor 2 to a
logic transistor (not shown) through the contacts 42 and the
interconnection 41.
Image sensor 100 includes multilayer structure 72 above
semiconductive substrate 1. Color filter array 73 is above
multilayer structure 72. Microlenses 741 are above color filter
array 73. Image sensor 100 includes interlayer dielectric (ILD))
layer 71 below semiconductive substrate 1. Redistribution layer 7
is below ILD layer 71.
The multilayer structure 72 includes a first transmitting layer
721, a second transmitting layer 722, and a capping layer 723. The
multilayer structure 72 is disposed over the back side S1 of the
semiconductive substrate 1. A bottom surface of transmitting layer
721 is in contact with a top surface of reflective material 82
within the DTI 86.
In some embodiments, the pixel array region 10 includes color
filter 731, 732, or 733 in color filter array 73 disposed proximate
to back side S1 of the semiconductive substrate 1. The back side S1
is opposite of the front side S2. In some other embodiments, the
multilayer structure 72 is arranged with an increasing refractive
index from air outside the image sensor 100 to the semiconductive
substrate 1.
In an embodiment, the semiconductive substrate 1 is made from
silicon. The semiconductive substrate 1 includes bulk silicon, a
semiconductor wafer, a silicon-on-insulator (SOI) substrate, or a
silicon germanium substrate. Other semiconductor materials
including group III, group IV, and group V elements are used in
some embodiments. The semiconductive substrate 1 is undoped in some
embodiments. Contact plug 53 is in contact with undoped regions in
semiconductive substrate 1. In some other embodiments, the
semiconductive substrate 1 is doped with a p-type dopant or an
n-type dopant. Doped regions such as the photo diodes are proximate
to contact plug 53. Back side S1 is at a top of the semiconductive
substrate 1. Front side S2 is at a bottom of the semiconductive
substrate 1.
Reflective material 82 is in the DTI 86 and borders with protective
layer 83. Reflective material 82 is in contact with multilayer
structure 72 near back side S1. Reflective material 82 serves as an
optical separation to configured pixel regions 17 and 18 such that
light would keep within each individual pixel region 17 or 18. In
some embodiments, reflective material 82 is made of a conductive
material. The conductive material is configured to reflect light.
Reflective material 82 is made of conductive materials such as
aluminum, copper, titanium nitride, tungsten, tantalum, tantalum
nitride, nickel silicide, cobalt silicide, other suitable
materials, and/or combinations thereof. The Reflective material 82
functions to prevent light from one pixel region 17 makes its way
into a neighboring pixel region 18, thereby causing the neighboring
pixel region 18 to sense the light by transistor 2.
In some embodiments, DTI 86 is replaced by a shallow trench
isolation (STI) features or a local oxidation of silicon (LOCOS)
features. The DTI 86 defines and isolates various elements or
regions from each other in the semiconductive substrate 1. For
example, the DTI 86 isolates adjacent pixel region 17 or 18 from
each other, the pixel array region 10 from black level reference
pixel 19, or some components of the circuitry inside a logic region
from each other. In some embodiments, a boundary between pixel
region 17 and 18 is void of DTI 86. In some embodiments, DTI 86 is
made of a dielectric material or insulator materials such as
silicon oxide, silicon nitride, or silicon oxynitride. In some
embodiments, the DTI 86 is a multi-layer structure including layer
such as a thermal oxide liner layer with silicon nitride or silicon
oxide inside the thermal oxide liner layer. In some embodiments,
reflective material 82 includes the silicon nitride or silicon
oxide.
In FIG. 2, semiconductive substrate 1 includes photosensitive
element 22, and photosensitive element 23 at a front side S2 of the
semiconductive substrate 1. Photosensitive element 22 and
photosensitive element 23 are above the front side S2 and within
semiconductive substrate 1. In some embodiments, photosensitive
elements 22, or 23 is a photo diode proximate to contact plug 53,
gate structure 21, or gate spacer 25.
In some embodiments, the photosensitive element 22 or the
photosensitive element 23 are a drain region or a source region. In
some embodiments, photosensitive element 22 or 23 is replaces by a
doped drain or source region. Photosensitive element 22 or 23 is
configured to receive light 8 (B, G or R). The light 8 is incident
upon a microlens 741, transmitted through color filter array 73 and
a multilayer structure 72, and traveled toward the back side S1
into the semiconductive substrate 1. The light 8 is then converted
by the photosensitive element 22, or 23 into electrical current.
The electrical current is transmitted through contact 42 and/or
contact plug 53 as image data.
Transistor 2 is connected with the photosensitive element 22 or 23
at a front side S2 of the semiconductive substrate 1. Transistor 2
includes a gate structure 21 and gate spacer 25 below front side
S2. An interconnection 41 coupled with the transistor 2 through a
contact 42. Interconnection 41 coupled with contact plug 53. In
some embodiments, the transistor 2 is a transfer transistor for
transferring the image data captured by a corresponding
photosensitive element 22 or 23 to external circuitry. In some
embodiments, additional transistors with various functions are also
included in each pixel array region 10. Other CIS arrangements are
suitable in some embodiments. The principles described herein are
also applicable to CCD pixels in further embodiments. In some
embodiments, other transistors in pixel array region 10 are
structured similarly to the transistor 2.
The ILD layer 71 is at front side S2. ILD layer 71 is below
semiconductive substrate 1. ILD layer 71 includes a height H4 from
front side S2 to redistribution layer 7. ILD layer 71 includes
dielectric layer 45 below front side S2. Contacts 42 and contact
plug 53 are buried inside dielectric layer 45. Contacts 42 are
connected with gate structure 21, photosensitive element 22, or
photosensitive element 23 of transistor 2. Contact plugs 53 are
coupled to non-salicide region 88. Non-salicide region 88 is a
portion of semiconductive substrate 1 void of dopant, metal,
salicide, or silicide. Non-salicide region 88 is also a silicon
portion. In some embodiments, non-salicide region 88 is proximate
front side S2.
Contact plug 53 is connected to the silicon portion of
semiconductive substrate 1. The silicon portion is composed of a
material void of metal, silicide, salicide, or dopant. The silicon
portion is a non-silicide portion. Contact plug 53 includes a
height H7. Contact plug 53 is partially buried inside the
semiconductive substrate 1 such that contact plug 53 is protruding
above ILD layer 71. In some embodiments, height H7 is larger than
height H4.
Contact plug 53 includes a silicide layer 50 at a top near front
side S2. Silicide layer 50 is in contact with front side S2.
Silicide layer 50 is inside semiconductive substrate 1. Silicide
layer 50 is distanced from back side S1 by a height H1. Front side
S2 is distanced from back side S1 by a height H2. DTI 86 is
distanced from front side S2 by a height H3. Silicide layer 50 is
distanced from reflective material 82 of DTI 86 by a height H5.
Height H1, H2, H3, H4, or H5 are measured vertically in a direction
orthogonal to front side S2 or back side S1.
Contact plug 53 includes silicide layer 50 inside non-salicide
region 88. In some embodiments, silicide layer 50 is composed of
self-aligned silicide (salicide). Silicide layer 50 is a salicide
layer 50 including a titanium element. The Silicide layer 50 is
above the front side S2 of the semiconductive substrate 1. Contact
plug 53 includes a barrier layer 51 in contact with silicide layer
50. In some embodiments, a thin film of conductive material such as
titanium is between barrier layer 51 and dielectric layer 45.
Barrier layer 51 includes any suitable conductive material such as
TiN, W, Ti, Mo, Co, Pt, TiW, Ta, TaN, TaSiN, or WN. In some
embodiments, harrier layer 51 serves as an adhesion promoter or a
diffusion barrier. The adhesion promoter provides suitable adhesion
strength between dielectric materials in dielectric layer 45 and
conductive material 52. The diffusion barrier serves to prevent
diffusion of materials inside conductive material 52. The diffusion
barrier serves to prevent intermixing of materials inside
conductive material 52 with material in silicide layer 50 or with
material in dielectric layer 45. In some embodiments, barrier layer
51 is a thin film between silicide layer 50 and conductive material
52. Conductive material 52 is inside contact plug 53. Conductive
material 52 is in contact with barrier layer 51. Barrier layer 51
is lined conformally to conductive material 52. Conductive material
52 is composed of any suitable material such as metal including W,
Ti, Cu, or Al. Contact plug 53 couples between interconnection 41
and semiconductive substrate 1.
Contacts 42 are connected to interconnection 41 in a redistribution
layer 7. Redistribution layer 7 is under the dielectric layer 45
and the contacts 42 in the ILD layer 71. The redistribution layer 7
includes an interconnection 41 coupled with the contacts 42. The
redistribution layer 7 includes alternating some conductive layers
and some dielectric layers 46. The conductive layers are patterned
and/or otherwise processed to form the interconnections 41 coupled
to some devices (e.g., the transistors 2) and/or between the
devices and some external circuitries. The interconnections 41 are
coupled to the devices through the contacts 42 or contact plugs 53.
The interconnection 41 is coupled to another interconnection 41 in
other layer through a via 43.
The contacts 42 are disposed in the dielectric layer 45. Contacts
42, contact plugs 53, or dielectric layer 45 are in the pixel array
region 10, or the black level reference pixel array 12. The ILD
layer 71 includes contact plug 53, the contacts 42, and the
dielectric layer 45. Contacts 42 are connected to photosensitive
element 22 or 23 at front side S2. Contacts 42 and contact plugs 53
are connected to interconnection 41 at an interface between ILD
layer 71 and redistribution layer 7. The inter-layer dielectric
(ILD) layer 71 is under the front side S2 of the semiconductive
substrate 1. The ILD layer 71 includes dielectric layer 45 made of
material such as, boron phosphorous silicate glass (BPSG), plasma
enhanced tetra-ethyl-ortho-silicate (PETEOS), or any other suitable
dielectric materials. In some embodiments, contact 42 or conductive
material 52 is made of materials such as aluminum, copper, titanium
nitride, tungsten, titanium, tantalum, tantalum nitride, nickel
silicide, cobalt silicide, TaC, TaSiN, TaCN, TiAl, TiAlN, other
suitable materials, and/or combinations thereof.
FIG. 3 illustrates image sensor 200 similar to the image sensor 100
in FIG. 2. The silicide layer 50 includes lateral portion P1, and
lower portion L1. In FIG. 3, barrier layer 51 is in between
silicide layer 50 and conductive material 52 inside contact plug
53.
In FIG. 3, contact plug 53 includes bottom side B1. A depth D1 of
contact plug 53 is measured from front side S2 to bottom side B1 of
contact plug 53. A height H1 is measured from back side S1 to
bottom side B1. A width W1 of contact plug 53 is measured from one
lateral side S21 of a contact plug 53 to another lateral side S21
of the same contact plug 53. An aspect ratio of contact plug 53 is
a ratio between height H7 and width W1.
Silicide layer 50 is a lower portion L1 of contact plug 53. Lower
portion L1 includes a bottom side B1. Lower portion L1 is bordering
with lower portion L2 of barrier layer 51 at bottom side B2. Bottom
side B2 is an interface between lower portion L1 and lower portion
L2. A distance between bottom side B2 and bottom side B1 is
thickness TH1 of silicide layer 50. In some embodiments, silicide
layer 50 includes a predetermined thickness TH1 proximately in a
thickness range from about 600 angstroms to about 1200 angstroms.
The thickness range is designed to a suitable range such that a
resistance of non-salicide region 88 is sufficiently small. In some
embodiments, thickness TH1 is smaller than depth D1 of contact plug
53. In other embodiments, thickness TH1 is substantially the same
as depth D1. In further embodiments, thickness TH1 is larger than
depth D1. Bottom side B1 includes a width W4. Bottom side B1
includes a surface substantially flat. Bottom side B1 and bottom
side B2 are substantially parallel with front side S2. Bottom side
B1 is in contact with semiconductive substrate 1 in some
embodiments, lateral side S21 of contact plug 53 is tapered such
that silicide layer 50 is in a trapezoidal shape and bottom side B1
is smaller than bottom side B2. In some other embodiments, a size
of bottom side B1 is substantially the same as a size of bottom
side B2. In some further embodiments, a size of bottom side B1 is
larger than a size of bottom side B2. Bottom side B2 extends from
one lateral side S21 to another lateral side S21. Bottom side B2 is
distanced from a top surface S71 of ILD layer 71 by a height H8. In
some embodiments, bottom side is under front side S2 such that
height H8 is greater than height H4 of ILD layer 71. In some other
embodiments, bottom side B2 is substantially coplanar with front
side S2 such that height H8 is substantially the same with height
H4 of ILD layer 71, in some further embodiments, bottom side B2 is
substantially above front side S2 such that height H8 is
substantially shorter height H4 of ILD layer 71. Contact plug 53
includes a lateral portion P1. Lateral portion P1 is compose of
metallic elements such as Ti.
Barrier layer 51 includes a lateral portion P2. Lateral portion P2
is lined to a lateral side S22 of conductive material 52. Lateral
side S22 is parallel with lateral side S21 of contact plug 53.
Lower portion L2 of barrier layer 51 is lined to bottom side 133 of
conductive material 52. Bottom side includes a width W5. In some
embodiments, barrier layer 51 is a thin film such that thickness of
lower portion L2 is small and an area of bottom side B3 is the same
as an area of bottom side B2. Width W5 is substantially larger than
or equal to width W4. Bottom side B3 is distanced from the top
surface S71 of ILD layer 71 by a height H9. Height H9 is a depth of
conductive material 52. Barrier layer 51 includes a width W2
measured along top surface S71. Top surface S71 is parallel with
front side S2. Width W2 is substantially the same as width W1. A
top of barrier layer 51 is in contact with interconnection 41.
Barrier layer 51 lined conformally on top of the silicide layer 50
near bottom side B2. In some embodiments, lateral portion P1 is a
thin film 511 lined to lateral portion P2 of barrier layer 51.
Conductive material 52 is partially surrounded by barrier layer 51
at bottom side B3 and at lateral side S22. Conductive material 52
is in contact with interconnection 41 at a top of conductive
material 52. Conductive material 52 includes a width W3 measured
along top surface S71. Conductive material 52 includes a top
surface S52 substantially coplanar with top surface S71. Top
surface S52 is an interface between conductive material 52 and
interconnection 41. In some embodiments, top surface S52 is larger
than bottom side B2 or bottom side B1. Conductive material 52 is a
conductive plug over the salicide layer such as silicide layer 50.
Width W4 of bottom side B1 is larger than, equal to, or smaller
than width W3 of conductive material 52. Bottom side B1 is an
interface between silicide layer 50 and non-salicide region 88 of
semiconductive substrate 1. A portion of semiconductive substrate 1
such as non-salicide region 88 surrounding silicide layers 50 is
void of metal or dopant.
Height H1, H2, H4, H7, H8, H9, depth D1, and thickness Th1 are
measured vertically in a direction orthogonal to front side S2.
Width W1, W2, W3, W4, W5, and W10 are measured horizontally in a
direction parallel with front side S2.
FIG. 4 illustrates image sensor 300 similar to the image sensor 200
in FIG. 3. In FIG. 4, the silicide layer 50 is a salicide layer
partially below the front side S2 of the semiconductive substrate 1
such that a bottom portion 510 below the front side S2 is larger
than a top portion 502 above the front side S2. Silicide layer 50
is partially buried in non-salicide region 88 of semiconductive
substrate 1. Thin film 511 is in contact with top portion 502 near
bottom side B2. In some embodiments, bottom side B2 is a top
surface of salicide layer 50. Thin film 511 is composed of metal
such as titanium. A top of thin film 511 is in contact with
interconnection 41.
In FIG. 4, silicide layer 50 includes a thickness TH1. Top portion
502 includes a thickness TH11. Bottom portion 510 includes a
thickness TH10. In some embodiments, thickness TH11 is smaller than
thickness TH10. Bottom portion 510 includes a width W4 at bottom
side B1. An interface between top portion 502 and bottom portion
510 is surface S7. Surface S7 includes a width W7 measured in a
direction along front side S2. An interface between top portion 502
and barrier layer 51 is bottom side B2. Bottom side B2 includes a
width W8. In some embodiments, width W8 is larger than width W7. In
some other embodiments, width W8 is equal to width 7. In some
further embodiments, width W8 is smaller than width W7. In some
embodiments, width W7 is larger than width W4. In some other
embodiments, width W7 is equal to width 4. In some further
embodiments, width W7 is smaller than width W4. In some
embodiments, width W8 is larger than width W4. In some other
embodiments, width W8 is equal to width W4. In some further
embodiments, width W8 is smaller than width W4. A difference
between width W8 and width W4 is width W84. Width W84 is measuring
how much lateral side S50 of silicide layer 50 is tapered.
Barrier layer 51 includes a lower portion L2 in contact with top
portion 502. Lower portion L2 includes a thickness TH2. In some
embodiments, thickness TH2 is substantially smaller than TH1 such
that a ratio between thickness TH1 and thickness TH2 is
substantially larger than 1. Barrier layer 51 includes lateral
portion P2. Lateral portion P2 includes a width W22. Width W22 is
substantially smaller than Width W4. In some embodiments, width W22
is substantially equals to thickness TH2.
Conductive material 52 is disposed conformally inside barrier layer
51. Conductive material 52 is bordered with lateral portion P2 and
lower portion L2. Conductive material 52 includes a height H9. In
some embodiments, height H9 is substantially larger than thickness
TH1, A top of conductive material 52 includes a width W3. In some
embodiments, height H9 is substantially larger than width W3 such
that contact plug 53 includes a high aspect ratio. In some
embodiments, width W3 is larger than width W8. In some other
embodiments, width W3 is equal to width 8. In some further
embodiments, width W3 is smaller than width W8.
FIG. 5 illustrates a lattice structure under X-ray crystallography.
X-ray crystallography is used for identifying lattice structures
similar to atomic structure 504 of a crystal, in which electrons of
atoms 503 cause a beam of incident rays 81 to diffract into many
specific directions. Incident ray 81 and diffracted ray 89 are
symmetric about a plane S57. Incident rays 81 are incident on plane
S55. By measuring angles in degree M1 and intensities of these
diffracted rays 89, a density of electrons within the crystal is
known. From the electron density, a mean distance of separation d
between planes S55 of the atoms in the crystal is determined.
Incident ray 81 and diffracted ray 89 includes a predetermined
wavelength. The incident rays 81 (coming from upper left) causes
each scatterer such as atoms 503 to re-radiate a small portion of
its intensity as a wave 821. Diffracted rays 89 are offset from
each other by a difference F. Difference F is derived from a
function: F=2 d sin(M1). For scatterers arranged symmetrically
about plane S57 and with a separation d between each plane S55,
waves 821 is in sync (add constructively) in a direction where
difference F equals to an integer multiple of the predetermined
wavelength. When in sync, intensity of wave 821 produces a peak in
a diffraction pattern. Atomic structure 504 includes other planes
such as plane S53. In some embodiments, plane S53 is a {110} plane
with separation D2 between planes S53. In some embodiments,
different planes with different length of separations produce
different peaks in the diffraction pattern.
X-ray crystallography is related to several other methods for
determining atomic structures 504. Similar diffraction patterns are
produced by scattering other wavelength of light, electrons, or
neutrons. To produce the diffraction pattern, the separation d
between the scatterers and the wavelength of an impinging wave such
as incident ray 81 are similar in size.
In FIG. 6, diffraction patterns 87 and 85 are illustrated. A
horizontal axis corresponds to a degree similar to degree M1 in
FIG. 5. A vertical axis corresponds to an intensity of diffracted
light waves similar to wave 821 in FIG. 5. Diffraction is used as
an analytical technique to characterize compounds or elements in
silicide layer 50 in FIG. 4, FIG. 3, or FIG. 2.
Different thickness TH1 of silicide layer 50 in FIG. 4, FIG. 3, or
FIG. 2 are analyzed by diffraction techniques and compared to one
another to determine different properties in different thickness of
silicide layer 50. For example, silicide layer 50 including
predetermined thickness TH1 proximately in the thickness range from
about 600 angstroms to about 1200 angstroms produces diffraction
pattern 87. Silicide layer 50 including predetermined thickness TH1
proximately smaller than the thickness range produces diffraction
pattern 85. Diffraction pattern 87 includes regions R1, R2, and R3.
Region R1 includes a peak corresponds to a {220} plane in a lattice
structure of silicide layer 50 in FIG. 4, FIG. 3, or FIG. 2. Region
R2 includes a peak corresponds to a {311} plane in the lattice
structure. Region R3 includes peaks corresponds to a {040} plane
and a {022} plane. Silicide layer 50 includes a lattice structure
with the {220} plane or the {311} plane measured with peaks on
X-ray diffraction pattern 87 of the lattice structure. Diffraction
patterns 87 and 85 of different thickness are different in regions
R1, R2, and R3. In some embodiments, region R4 includes minor peaks
correspond to the {040} plane and the {022} plane. However, those
minor peaks are substantially smaller in intensity compare with
peaks in region R3.
In FIG. 7, a method of manufacturing 400 is illustrated. FIG. 7
illustrates a process flow for forming the image sensor 100, 200,
or 300 in FIG. 2, 3, or 4. Operation 410 receives a semiconductive
substrate 1. Some exemplary embodiments for operation 410 are
illustrated in FIG. 9. Operation 420 forms a dielectric layer 45 on
a front side S2 of the semiconductive substrate 1. Some exemplary
embodiments for operation 420 are illustrated in FIG. 10. Operation
430 forms a recess 55 in the dielectric layer 45. Some exemplary
embodiments for operation 430 are illustrated in FIG. 11. Operation
440 forms a conductive layer 501 inside the recess 55 and on the
front side S2 of the semiconductive substrate 1. In some
embodiments, the conductive layer 501 is a titanium layer 501. Some
exemplary embodiments for operation 440 are illustrated in FIGS. 12
and 13. Operation 450 performs a first thermal anneal. Some
exemplary embodiments for operation 450 are illustrated in FIG. 14.
Operation 460 performs a second thermal anneal. Some exemplary
embodiments for operation 460 are illustrated in FIG. 15.
In FIG. 8, operation 440 in method of manufacturing 400 in FIG. 7
is expanded to include operations 441, 442, and 443. Operation 441
uses a plasma ignition power in a predetermined range D11 from
about 600 watts to 900 watts to form a conductive layer 501 inside
the recess 55 and on the front side S2 of the semiconductive
substrate 1. Operation 442 uses a first plasma power maintained
substantially constant at a first predetermined range D12 lesser
than half of the predetermined range D11 to form a conductive layer
501 inside the recess 55 and on the front side S2 of the
semiconductive substrate 1. Operation 442 uses a second plasma
power maintained substantially constant at a second predetermined
range D17 proximately double the first predetermined range D12 but
lower than the predetermined range D11 to form a conductive layer
501 inside the recess 55 and on the front side S2 of the
semiconductive substrate 1. Some exemplary embodiments for
operations 441, 442, and 443 are illustrated in FIG. 13.
In FIG. 9, the semiconductive substrate 1 is received. In some
embodiments, semiconductive substrate 1 includes an isolation
region (not shown) formed by etching a trench in the semiconductive
substrate 1 on the front side S2 and filling the trench with
insulator materials such as silicon oxide, silicon nitride, or
silicon oxynitride.
A gate dielectric layer 213 is covering over the semiconductive
substrate 1. A gate electrode layer 214 is formed on top of gate
dielectric layer 213 by any suitable deposition.
The deposition processes include chemical vapor deposition (CVD),
physical vapor deposition (PVD), atomic layer deposition (ALD),
high density plasma CVD (HDPCVD), metal organic CVD (MOCVD), remote
plasma CVD (RPCVD), plasma enhanced CVD (PECVD), low-pressure
chemical vapor deposition (LPCVD) process, thermal oxidation,
UV-ozone oxidation, epitaxial growth methods (e.g., selective
epitaxy growth), sputtering, plating, spin-on coating, other
suitable methods, and/or combinations thereof. The gate electrode
layer 214 is deposited above the front side S2 of the
semiconductive substrate 1.
The gate dielectric layer 213 and the gate electrode layer 214 are
patterned by a photolithographic process. In the photolithographic
process, a layer of resist 35 is formed on top of gate electrode
layer 214 and patterned to form a resist feature by a
photolithography patterning method. The resist feature can then be
transferred by an etching process 32 to some underlying layers gate
electrode layer 214 or gate dielectric layer 213).
The etching process 32 is any suitable etching process such as dry
etching, wet etching, reactive ion etching (RIE), and/or other
etching methods. The etching process 32 is either purely chemical
(plasma etching), purely physical (ion milling), and/or
combinations thereof.
The resist feature is transferred to gate dielectric layer 213 and
gate electrode layer 214 to form gate structure 21 on a front side
S2 of the semiconductive substrate 1 in FIG. 10. Gate spacer 25 is
formed using any suitable process, including some processes
described herein.
In FIG. 10, transistor 2 is formed coupling to photosensitive
element 22 or 23 at front side S2 of the semiconductive substrate
1. In some embodiments, photosensitive element 22 or 23 is a source
or a drain region formed by ion implantation or epitaxially
growth.
In FIG. 10, the dielectric layer 45 is covering over the
semiconductive substrate 1 by any suitable process such as the
deposition process. Dielectric layer 45 is formed on front side S2
of the semiconductive substrate 1. The dielectric layer 45 is in
contact with front side S2 and gate structure 21. A resist 31 is
formed on top of surface S45 of the dielectric layer 45. Some
etching process 32 is performed to transfer a patterned resist
feature to the dielectric layer 45. The resist features includes
openings with width W1.
In FIG. 11, the patterned resist feature is transferred to
dielectric layer 45 to form recess 55. In some embodiments, the
recesses 55 are formed by any suitable etching process such as the
selective etching, the dry etching, and/or combination thereof. The
selective etching uses some fluorine-containing gas, HBr and/or Cl2
as etch gases. In some embodiments, the selective etching includes
a faster etching rate for materials in dielectric layer 45 than for
materials in semiconductive substrate 1. Different etchant can be
used for etching different compositions of materials.
Recess 55 is formed such that surface S72 of semiconductive
substrate 1 is exposed near a bottom of recess 55. In some
embodiments, surface S72 is below front side S2 by a depth similar
to thickness TH14. Surface S72 includes a width W9. In some
embodiments, a size of surface S72 is smaller than a size of
surface S7 in FIG. 4. Width W9 is smaller than width W7 in FIG. 4.
A top of recess 55 includes a width W11. Width W11 is substantially
the same as width W1 of contact plug 53 in FIG. 3. Width W11 is
measured along surface S45. After the recess 55 is formed resist 31
is removed.
In FIG. 12, conductive layer 501 is formed on top of dielectric
layer 45 and covered over recess 55. A top portion T of conductive
layer 501 is over surface S45 of dielectric layer 45. Conductive
layer 501 is conformally formed over recess 55 such that recess 57
is formed following a contour of recess 55. Lateral side S of
conductive layer 501 is lined to a lateral side of recess 55. In
some embodiments, recess 57 is aligned vertically over recess
55.
In some embodiments, bottom portion B5 or B4 of conductive layer
501 is formed near front side S2. Bottom portion B5 is over front
side S2. Bottom portion B4 is under front side S2. Bottom portion
B5 of conductive layer 501 includes a thickness TH501 measured
vertically in a direction orthogonal to front side 52. Bottom
portion B4 of conductive layer 501 includes a thickness TH14
measured vertically in a direction orthogonal to front side S2.
Thickness TH14 is measured from front side S2 to surface S14.
Bottom portion B4 includes a surface S14 in contact with
non-salicide region 88. Bottom portion B4 is buried inside
non-salicide region 88. Surface S14 includes a width W15. In some
embodiments, width W15 is different from width W4 in FIG. 4. In
some embodiments, bottom portion B4 is substantially a thin film
such that thickness TH14 is smaller than thickness TH15. A bottom
of recess 57 exposes a top side of bottom portion B5. The top side
is exposed and includes a width W17. A top of recess 57 includes a
width W18. Width W17 is smaller than width W18.
In some embodiments, thickness TH14 is substantially larger than
thickness TH15. An interface is between bottom portion B5 and
bottom portion B4. The interface includes a width W9 measured in a
direction along front side S2. In some embodiments, width W9 is
larger than width W15. In some other embodiments, width W9 is equal
to width 15. In some further embodiments, width W9 is smaller than
width W15. In some embodiments, width W17 is smaller than or equal
to width W18. In some embodiments, width W17 is equal to width W9.
In some further embodiments, width W17 is equal to width W15.
Conductive layer 501 is formed by any suitable method such as
deposition operation 331 or epitaxial growth. The deposition
operation 331 includes any suitable operation such as sputtering
deposition, physical vapor deposition (PVD)), high density plasma
CVD (HDPCVD), remote plasma CVD (RPCVD), plasma enhanced CVD
(PECVD), sputtering, other suitable methods, and/or combinations
thereof.
FIG. 13 is a diagram 110 illustrated a trace 114 of a plasma power
used during the deposition operation 331 to form conductive layer
501 in FIG. 12. A horizontal axis of diagram 110 represents
duration of the deposition operation 331. A vertical axis of
diagram 110 represents a power applied to plasma.
In some embodiments, deposition operation 331 is a PVD operation
using sputtering to deposit titanium (Ti). The PVD operation
includes creating plasma and using plasma to erode a target (not
shown). A material in the target is hit by plasma and deposited on
a wafer (not shown). In the PVD operation, a vacuum is created in a
chamber (not shown) to a certain low pressure. Argon (Ar) is
introduced into the chamber. The Ar is then ignited to form a
plasma of Ar+ ions. In some embodiments, the target is made of
titanium. During deposition, the target is biased negatively,
causing positively charged Ar+ ions to bombard the target. The
positively charged Ar+ ions knock target atoms from the target. The
target atoms are then propelled towards the wafer. The plasma in
the chamber is created by applying a voltage across the target to
the plasma ignition power level. The plasma ignition power is
referred to as a "break down" spike. The break down spike is
associated with a creation of a plasma in the chamber (also known
as "plasma ignition"). This condition creates an initial thin layer
near surface S14 under front side S2 in FIG. 12. In some
embodiments, the plasma ignition power is limited to predetermined
range D11 such that the initial thin layer is formed to be
substantially smooth.
A power of plasma is corresponded to a depth of a deposited
material inside the wafer. The power of plasma is corresponded to a
thickness of the deposited layer on the wafer. For example, an
increased plasma power increases a depth of deposited material
buried in the wafer. In some embodiments, plasma is generated in a
region above the wafer and between the wafer and the target, and
cause material from the target to deposit on the wafer such as on
surface S45 in FIG. 12.
In diagram 110 trace 114 in stage S441 rise sharply to reach the
plasma ignition power. In some embodiments, the plasma ignition
power is in a predetermined range D11 from about 600 watts to 900
watts. Then trace 114 drops down by power level D14 to first
predetermined range D12. First predetermined range D12 is about
half of the predetermined range D11. Predetermined range D11 from
about 600 watts to 900 watts is to prevent roughness the initial
thin layer near surface S72 in FIG. 11. Surface S72 in FIG. 11 is
deposited by any suitable deposition operation to form surface S14
in FIG. 12. A smoothness of the initial thin layer affects a
conductivity of non-salicide region 88 in FIG. 12, and reduces
resistance between non-salicide region 88 and bottom portion B4 in
FIG. 12.
In stage 442, the PVD operation uses a first plasma power
maintained substantially constant at first predetermined range D12.
In some embodiments, first predetermined range D12 is lesser than
half of the predetermined range D11. Stage S442 last substantially
longer than stage S441.
In stage S443, the PVD operation uses a second plasma power
maintained substantially constant at second predetermined range
D17. In stage S443, trace 114 rises to second predetermined range
D17. Second predetermined range D17 is proximately double the first
predetermined range D12 but lower than the predetermined range D11.
Second predetermined range D17 is lower than predetermined range
D11 by a power level D18. Second predetermined range D17 is larger
than first predetermined range D12 by a power level D15.
In FIG. 14, image sensor 500 is heated in a first thermal anneal
such as a first rapid thermal anneal (RTA) operation. Performing
the first thermal anneal causes a material, such as titanium, in
bottom portion B4 or bottom portion B5 to react with non-salicide
region 88 in semiconductive substrate 1 to form silicide layer 50.
However, conductive layer 501 deposited on surface S45 or near
lateral side S27 of recess 57 does not react to form silicide.
In some embodiments, silicide layer 50 is expanded such that a size
of silicide layer 50 is larger than bottom portion B4, bottom
portion B5, and/or combination thereof in FIG. 12. Width W4 is
larger than width W15 in FIG. 12. Thickness TH1 is larger than
thickness TH15, thickness TH14, and/or combination thereof in FIG.
12. Width W7 is larger than width W9 in FIG. 12. Silicide layer 50
includes a thickness TH17 measured from front side S2 to a bottom
side B1. In some embodiments, thickness TH17 is larger than
thickness TH14 in FIG. 12.
In FIG. 15, silicide layer 50 is tapered such that width W4 is
smaller than a top side of silicide layer 50 by a width W8. In FIG.
15, material such as unreacted titanium in conductive layer 501 in
FIG. 14 is selectively etched from the surface S45 or close to
lateral side S28 of recess 58 leaving silicide layer 50 near front
side S2. Removing the unreacted titanium is performed between the
first thermal anneal and the second thermal anneal. The material in
silicide layer 50 such as reacted titanium silicide (TiSi2) has a
crystallographic structure, known as C49. C49 TiSi2 has a high
sheet resistance.
In some other embodiments, the unreacted titanium is remained
inside recess 58 and lined to lateral side S28. A second thermal
anneal such as a second RTA is performed to cause C49 TiSi2 to
change phase, forming a low resistance C54 TiSi2. C54 TiSi2 has a
lower sheet resistance than C49 and is used as an effective contact
material. C54 TiSi2 has a low contact resistance property. In FIG.
6, diffraction patterns 87 and 85 include planes in the lattice
structure of C54 TiSi2 as shown in region R1, R2, R3, or R4. After
performing the second thermal anneal, salicide layer 50 includes a
lattice structure of C54 with a {220} plane, a {040} plane, a {022}
plane, or a {311} plane measured with peaks on an X-ray diffraction
pattern 87 of the lattice structure.
By performing the second thermal anneal, silicide layer 50 is
formed including a predetermined thickness proximately in a range
from about 600 angstroms to about 1200 angstroms. In some
embodiments, a size of silicide layer 50 is changed by the second
thermal anneal.
In some other embodiments, silicide layer 50 is planarized such
that a top of silicide layer 50 is coplanar with front side S2, and
thickness TH1 is measured from front side S2 to bottom side B1. In
some further embodiments, the first thermal anneal or the second
thermal anneal is performed in later operations such as after
conductive material 52 is formed over barrier layer 51 in FIG.
17.
In FIG. 16, barrier layer 51 is conformally deposited covering over
recess 58 and silicide layer 50. Barrier layer 51 is formed on top
of surface S45 and silicide layer 50 to form recess 59 over recess
58. Barrier layer 51 is formed by any suitable method of
deposition. In some embodiments, thin film 511 of unreacted metal
such as titanium is remained and conformally lined to a lateral
side S28 of recess 58. Barrier layer 51 is covering over thin film
511 conformally.
In FIG. 17, recesses 59 are filled by conductive material 52 in
some suitable processes such as the deposition process. Conductive
material 52 is formed on top of barrier layer 51. The process
parameters include a total pressure, some reactant concentrations,
a deposition temperature, or a deposition rate.
In FIG. 18, a top portion of conductive material 52 and barrier
layer 51 are removed by any suitable planarization such as a
chemical mechanical planarizing CMP or etching back. Planarization
is performed such that surface S45 is exposed. Planarization is
performed such that a top of conductive material 52 is
substantially coplanar with surface S45.
In FIG. 19, contact plug 53 is formed. In FIG. 19, resist 31 is
formed on top of surface S45. The resist feature is transferred to
dielectric layer 45 to form contact 42 in FIG. 20. In FIG. 20, the
patterned resist feature is transferred to dielectric layer 45 to
form some trenches 422. In some embodiments, the trenches 422 are
formed by any suitable etching process such as the selective
etching, the dry etching, and/or combination thereof. The trenches
422 are filled by some conductive materials to form contacts 42.
Contacts 42 are formed by filling the trenches 422 by some suitable
processes such as the deposition operation. The deposition
operation covers over surface S45 to form conductive layer 411.
Conductive layer 411 is formed over conductive material 52 and on
top of ILD layer 71.
In FIG. 21, conductive layer 411 is patterned by any suitable
lithographic operation to form interconnection 41. Interconnection
41 is formed on top of conductive material 52 to electrically
coupled silicide layer 50 to other circuitry. Interconnection 41 is
formed on top of contact 42 to electrically coupled contact 42 to
other circuitry.
In FIG. 22, dielectric materials are covering over the
interconnections 41 to form dielectric layer 46 by some suitable
deposition operation. Dielectric layer 46 is patterned and etched
to form recesses. The recesses are filled by conductive material to
form via 43. In some embodiments, a planarization, such as chemical
mechanical planarizing CMP, is used to remove some excess blanket
layers of the conductive materials of via 43. Additional layer of
interconnection 41 is formed in a similar fashion as a first layer
of interconnection 41. In some embodiments, dielectric layer 46 is
covering over the vias 43 and over interconnection 41.
In FIG. 23, image sensor 500 is flipped upside down such that the
back side S1 of the semiconductive substrate 1 is above the front
side S2. Multilayer structure 72 is formed on top of the back side
S1. Transmitting layer 721 and second transmitting layer 722 are
formed sequentially by the deposition processes such as CVD, PECVD,
or other suitable methods. Light shielding layer 752 is formed on
top of multilayer structure 72 by depositing and patterning light
shielding layer 752. The light shielding layer 752 is formed by the
deposition process including depositing a metal layer (or a layer
of another opaque material) over the second transmitting layer 722.
The deposited layer is etched to leave the light shielding layer
752 in a region corresponding to the black level reference pixels
19.
Black level reference pixels 19 is formed by forming the light
shielding layer 752 on the second transmitting layer 722. The
capping layer 723 is blanket formed over the light shielding layer
752 and the second transmitting layer 722. In some embodiments,
capping layer 723 is a passivation layer.
A color resist 742 is formed over the multilayer structure 72. The
color resist 742 is for allowing a light with a color red, green,
or blue to pass through. The color resist 742 is formed by any
suitable process such as a deposition process. The deposition
process may be spin-on coating, chemical vapor deposition (CVD),
physical vapor deposition (PVD), atomic layer deposition (ALD), or
combination thereof.
A suitable process such as photolithography is performed on the
color resist 742. In photolithography the color resist 742 is
exposed through a photomask 37. A photomask 37 is patterned to
include a region 38. The region 38 forms a pattern over a portion
732 of color resist 742 in pixel region 18. The photomask 37 is
placed over the color resist 742 to allow ultraviolet (UV) light 39
reaching to portion 732 of the color resist 742 under the region
38. The color resist 742 is photosensitive. To make the pattern
insoluble, the portion 732 is UV cured by exposure through region
38 of photomask 37. Other soluble portions of the color resist 742
are removed by a developing solution. The pattern is cured through
baking. The portion 732 is hardened, insoluble and remained on top
of the multilayer structure 72 after baking.
In FIG. 24, the portion 732 remained is a color filter 732. The
color filter 732 is aligned within the pixel region 18. Color
filter 731 and a color filter 733 are formed sequentially by a
similar operation as the operation for forming the color filter
732, except that a different color resist is used.
In FIG. 25, microlenses 741 are formed on top of color filter array
73. Microlenses 741 are formed aligned vertically with color filter
732 or color filter 731.
Some embodiments of the present disclosure provide a back side
illuminated (BSI) image sensor. The back side illuminated (BSI)
image sensor includes a semiconductive substrate and an interlayer
dielectric (ILD) layer at a front side of the semiconductive
substrate. The ILD layer includes a dielectric layer over the
semiconductive substrate and a contact partially buried inside the
semiconductive substrate. The contact includes a silicide layer
including a predetermined thickness proximately in a range from
about 600 angstroms to about 1200 angstroms.
Some embodiments of the present disclosure provide a back side
illuminated (BSI) image sensor. The BSI image sensor includes a
semiconductive substrate including a silicon portion and an
interlayer dielectric (ILD) layer at a front side of the
semiconductive substrate. The ILD layer includes a dielectric layer
on the front side and a contact plug surrounded by the dielectric
layer and partially buried inside the silicon portion. The contact
plug includes a salicide layer including a lattice structure. The
lattice structure includes a {220} plane or a {311} plane
configured to be measured with peaks on an X-ray diffraction
pattern of the lattice structure.
Some embodiments of the present disclosure provide a method of
manufacturing a hack side illuminated (BSI) image sensor. The
method includes receiving a semiconductive substrate; forming a
dielectric layer on a front side of the semiconductive substrate;
forming a recess in the dielectric layer such that the front side
is exposed; forming a titanium layer inside the recess and under
the front side of the semiconductive substrate by using a plasma
ignition power in a predetermined range from about 600 watts to 900
watts; performing a first thermal anneal; performing a second
thermal anneal; and forming a barrier layer inside the recess.
The foregoing outlines features of several embodiments so that
those skilled in the art may better understand the aspects of the
present disclosure. Those skilled in the art should appreciate that
they may readily use the present disclosure as a basis for
designing or modifying other processes and structures for carrying
out the same purposes and/or achieving the same advantages of the
embodiments introduced herein. Those skilled in the art should also
realize that such equivalent constructions do not depart from the
spirit and scope of the present disclosure, and that they may make
various changes, substitutions, and alterations herein without
departing from the spirit and scope of the present disclosure.
* * * * *